[FFmpeg-devel] [FFmpeg-devel-irc] IRC log for 2010-09-08

[Michael Karcher]

Am Donnerstag, den 09.09.2010, 18:02 -0400 schrieb Ronald S. Bultje:
> Hi,
> 
> On Thu, Sep 9, 2010 at 5:52 PM, Reimar D?ffinger
> <Reimar.Doeffinger at gmx.de> wrote:
> > On Thu, Sep 09, 2010 at 05:22:10PM -0400, Ronald S. Bultje wrote:
> >> Our inline asm has huge issues on Win64, many which
> >> cannot be easily fixed.
> >
> > That I just don't see.
> 
> As you know (you were the first to provide a patch for this), xmm6 and
> xmm7 on Win64 are callee-save.
> 
> This means that any such construct...
> 
> void function()
> {
>  asm("movd $0, xmm7\r\n", mem);
>  //something else
>  asm("movd xmm7, $0\r\n", mem);
> }
> 
> ...cannot possibly be made to work. Putting xmm7 in the clobberlist
> doesn't preserve its value between asm() blocks, and not doing so
> screws up the caller's original xmm7 value.

What about using a variable with an xmm-reg constraint instead of
hardcoding xmm7 and have gcc allocate it (and care about
spilling/preserving)?

Regards,
  Michael Karcher